This isn't 'fun' exactly but I'm always fascinated to be reminded that everything in our lives that we take for granted was made up by someone for the first time.

"Guido of Arezzo was an 11th-century Benedictine monk and Italian music theorist. During his time at the abbey, he realized singers needed a faster, easier way to memorize the chants that so often saturated the hallowed air. Guido crafted a system that used lines, clef signs, and colors to indicate the pitch, which transformed music into information that could be read and stored in a book rather than solely tucked away in one’s mind. As the inventor of modern staff notation, he became a musical revolutionary."

There's more to the story... his work wasn't appreciated by his fellow monks...

Pomposa Abbey (Italy) The birthplace of modern musical notation — by StepYoshi

https://www.atlasobscura.com/places/pomposa-abbey